Electrical parts such as memory modules are generally constructed by positioning semiconductor chips on a daughter board. Such electrical parts have terminal portions with terminals aligned in a predetermined pitch at the edge of the daughter board. Among them, ones having semiconductor chips disposed on both sides of the daughter board, and having terminals formed on both sides of the terminal portion, are called DIMM, and have formed the a mainstream of memory modules in recent years.
To dispose the above electrical parts on packaging boards such as CPU boards, electrical connector having slit-like receiving slots for receiving terminal portions of electrical parts are used. As such electrical connectors, ones having two electrical part-receiving slots which enable them to receive terminal portions of two pieces of electrical parts, have been known, by which the number of parts disposed on the packaging board can be reduced.
When, for example two pieces of memory modules are positioned, it is necessary in many cases to connect the terminals of signals common to two pieces of memory modules, such as a data bus, together to the corresponding circuits of a packaging board, and at the same time, to connect terminals of different signals such as row address select signals separately to the corresponding circuits of the packaging board. In such an instance, the above electrical connector having two electrical part-receiving slots is used. Otherwise, two usual electrical connectors each having one electrical part-receiving slot are used, and the two pieces of electrical parts are separately connected to the two corresponding circuits of the packaging board, and then the two corresponding circuits are connected with common wiring on the packaging board to accomplish the electrical connection.
FIGS. 4(a) and 4(b) show electrical connectors disclosed in Japanese Unexamined Patent Publication No. 8-171966. FIG. 4(a) is a cross-sectional view taken along the portion where independent terminals are arranged, and FIG. 4(b) is a cross-sectional view taken along the portion where common terminals are arranged.
As shown in FIGS. 4(a) and 4(b), the conventional electrical connector 100 has a structure having an insulating housing 110 and two slit-like electrical part-receiving slots 120, 130 disposed in an upright two-stage style, to each of which a terminal portion 210 of an electrical part 200 is inserted.
On opposed inner walls 121, 122, 131, 132 of the electrical part-receiving slots 120, 130, a plurality of grooves are formed in an alignment pitch corresponding to the terminals. To these grooves, a pair of independent terminals 140, 150 as shown in FIG. 4(a) or a common terminal 160 as shown in FIG. 4(b) are inserted.
As shown in FIG. 4(a), one independent terminal 140 has a contact portion 141 which extends along the upper inner wall 121 of the upper electrical part-receiving slot 120, a locking portion 142 to the housing 110, and a leg portion 143 which protrudes from the bottom portion of the rear face side of the housing 110. Further, another independent terminal 150 has a contact portion 151 which extends along the upper inner wall 131 of the lower electrical part-receiving slot 130, a locking portion 152 to the housing 110, and a leg portion 153.
Further, as shown in FIG. 4(b), the common terminal 160 has a first contact portion 161 which extends along the lower inner wall 122 of the upper electrical part-receiving slot 120, a second contact portion 162 which extends along the lower inner wall 132 of the lower electrical part-receiving slot 130, a locking portion 163 to the housing 110, and a leg portion 164.
The leg portions 143, 153, 164 of respective terminals 140, 150, 160, are connected to the wiring of a packaging board 300 by, for example, soldering. In this case, a terminal of signals common to two pieces of electrical parts, such as a data bus, are connected to the corresponding circuit of the packaging board 300 through the common terminal 160, and at the same time, terminals of different signals, such as a row address select signal, are separately connected to the corresponding circuits of the packaging board through the independent terminals 140, 150.
However, when such an electrical connector is disposed on the packaging board, since the electrical part-receiving slots to which two pieces of the electrical parts are inserted are constructed in an upright two-stage style as mentioned above, there is a problem that the height of installation of the electrical connector on the packaging board is higher than that of the case where an electrical connector to which only one piece of electrical part is inserted is disposed. Accordingly, if such an electrical connector is disposed on a CPU board of e.g. a note-type personal computer (a portable type personal computer), the height of installation of the electrical connector on the CPU board is too high, and it will be difficult to make the note-type personal computer sufficiently thin.